1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing an impeller of a pump, and more particularly to an apparatus and a method for manufacturing an impeller in which a body of the impeller and a shroud are joined together by a twisting vibration.
2. Prior Art
A pump 1 used in a system for discharging or circulating fluid has, as shown in FIG. 1, a motor housing 3 for accommodating a motor assembly and a pump housing 2 for accommodating water. The motor assembly installed in the motor housing 3 comprises a stator 8, a rotor 7, and a rotational shaft 9 inserted to the rotor 7 by force. The rotational shaft 9 is supported by a first bearing 5 and a second bearing 6. At the end part of the rotational shaft 9, an impeller 10 is assembled. The impeller 10 is disposed in the pump housing 2.
When the motor assembly is supplied with electric power, the rotor 7 is rotated by the magnetic force generated between the rotor 7 and the stator 8, and then the rotational shaft 9 and the impeller 10 assembled with the rotational shaft 9 are rotated by the rotor 7. When the impeller 10 is rotated, the water accommodated in the pump housing 2 is pumped out. Part of the water flows into the motor assembly through the first bearing 5, and then the rotor 7 and the stator 8 are cooled thereby.
FIG. 2 is an enlarged exploded side sectional view of an impeller installed into the pump in FIG. 1. The impeller 10 is rotated by the motor assembly to discharge the water flowed in the housing. The impeller 10 comprises a body 11 and a shroud 13. The body is formed with a plurality of vanes 12 (or wings) and a boss 11a. The shroud 13 is joined with the vanes 12 of the body 11. When the impeller 10 rotates, the water in the pump housing 2 flows, as designated by the direction of the arrows, in through the opening of the shroud 13, and then it is discharged through the side part of the vanes 12.
Such an impeller is manufactured with engineering plastic or noryl, and the shroud 13 and the body 11 are joined by ultrasonic welding or abrasive fusing by rotation.
However, although the ultrasonic welding is an appropriate method for joining the circular elements like the impeller 10, the material which can be joined by the ultrasonic welding is confined to a few materials, so there is a shortcoming that the choice of material to improve the performance of the impeller 10 is restricted.
Furthermore, according to the abrasive fusing by rotation, since the edge of the vane 12 is narrow, there is a problem that a lot of burr is generated at the joining part thereof. That is because the rotational abrasive fusing is a proper method for the elements in which the surfaces to be joined are plane, and is not a proper method for the impeller 10 which should be manufactured by joining the plane surface of the shroud 13 with the edge part of the vane 12. If the burr is generated, the additional process for eliminating the burr is required, so the manufacturing process of the impeller 10 becomes complex. Further, if the burr is not eliminated sufficiently, it hinders the flow of water circulated via the motor assembly, whereby the cooling efficiency of the motor assembly is lowered and the overheating of the motor assembly occurs.